International Journal of Agriculture and Forestry 2015, 5(2): 79-91 DOI: 10.5923/j.ijaf.20150502.02 Floristic Composition, Affinities and Plant Formations in Tropical Forests: A Case Study of Mau Forests in Kenya Festus M. Mutiso1,*, Mware J. Mugo2, Joshua Cheboiwo3, Francis Sang4, George K. Tarus5 1South Eastern Kenya University, School of Environment & Natural Resources Management, Kitui, Kenya 2Karatina University, School of Environmental Studies and Natural Resources Management, Karatina, Kenya 3Kenya Forestry Research Institute, Londiani, Kenya 4University of Eldoret, School of Natural Resources Management, Eldoret, Kenya 5Kenya Forest Service, Nairobi, Kenya Abstract In the past, Mau forest complex has faced a wide range of disturbances majorly anthropogenic in nature. In this paper, the ecosystem floristic composition, richness, diversity and affinities are evaluated. Diameter at breast height (dbh) was measured and types and levels of disturbances recorded in plots, dbh of saplings measured in subplots and seedlings counted in microplots. To obtain the floristic composition and richness, we categorized species based on their families, development stages and life forms. Shannon-Wiener information index (H’) and Jaccard (JIA) and Sorensen(S) similarity indices were used to evaluate the species diversity and similarity respectively Trees, recorded belonged to 52 species, 45 genera and 31 families for seedlings; 43 species, 38 genera and 29 families for saplings and 55 species, 48 genera and 31 families for mature trees. The most species-rich family was rutaceae with six species followed by moraceae and flacourtiaceae with five. Western Kedowa had the highest diversity. Northern and Western Kedowa were the most similar pairs. Past and present disturbances and aggressive proliferation of the invasive; Trichocladus ellipticus (Eckl. and Zeyh) are the main causes of low species diversity and richness. In conclusion, the sites are floristically dissimilar but at varying degrees. The post-disturbance recovery on different sites is following different trajectory successional pathways. We recommend that the on-going disturbances should be curtailed to promote regeneration and successful recruitment of non-pioneer species. Keywords Tropical forests, Mau ecosystem, Floristic composition, Species richness, Diversity and similarity indices resilience and sustainability. Gaaf [7], Finegan and Camacho 1. Introduction [8] and Kumar [9] cautioned that post-disturbance departure from natural regeneration patterns is detrimental to future The disappearance of tropical forests at an estimated rate ecosystem sustainability. It is important to note that of 1 - 2% per year comes at a time when our knowledge of disturbances are part of ecosystem and they shape the their structure, composition, dynamics, diversity and structure and function of natural ecosystem. Sapkota et al. taxonomy has been not fully unraveled [1]. Similar [10] states that disturbance is a management tool and that concerns are expressed by Swamy et al. [2] who assert that moderate disturbance is believed to enhance diversity though the disappearance of the tropical forests comes at a time not all disturbances are helpful. Under normal disturbance when our knowledge on their structure and functional conditions, shift in species composition typically occurs dynamics is woefully inadequate. Kharkwal et al. [3] opine slowly in natural forests [11]. that accelerated species loss could lead to collapse of some Mutiso et al. [12] cite alteration of cyclic and parallel ecosystems. Successful implementation of ecosystem configuration processes of the Mau ecosystem by management requires strategic forest management planning, disturbances and its implication on future stand resilience. It including the ability to forecast future forest composition is important for forest managers to identify and understand [4]. Predicting plant community compositional change is a post-disturbance stand successional trajectory pathways. key challenge for ecologists and resource managers [5, 6]. This enables the managers to isolate different plant Understanding post-disturbance stand composition and plant formations representing different management units with formations give insights into the future ecosystem integrity, botanical uniqueness [13]. Management should take action against large-scale post-disturbance departure from natural * Corresponding author: [email protected] (Festus M. Mutiso) successional pathways. It is, however, worth to note that any Published online at http://journal.sapub.org/ijaf action taken to aid in rehabilitation should mimic the natural Copyright © 2015 Scientific & Academic Publishing. All Rights Reserved processes ([14], [8] and [15]). Sovu et al. [16] and Sovu [17] 80 Festus M. Mutiso et al.: Floristic Composition, Affinities and Plant Formations in Tropical Forests: A Case Study of Mau Forests in Kenya state that enrichment planting is the preferred method of the future ecosystem integrity, resilience and sustainability at assisting natural regeneration of degraded forests when stake. The gradients in revegetation and pulses in desirable species are absent or at low densities. Similarly, regeneration as observed in Mau [12] are worth investigating. Satoka et al. [10] suggested enrichment planting as a way of Rydgreen et al. [29] stress the importance of understanding restoring the under-populated tree species. Further, Bergeron the full complexity of revegetation and processes following et al. [18] stress the importance of forest management based disturbances. on natural disturbances to cushion ecosystems against Kittur et al. [11] noted reduced structural and biological collapse. Post-disturbance lack of species co-existence under complexity in natural forest due to fire severity. Sovu [17] natural regimes [19] and individualistic successional stated that the success of recovery depends on the severity pathways ([4] and [12]) should be identified. Management and intensity of disturbances. Further, Frelich et al. [30], need to understand the ecosystem threshold responses after Taylor et al. [4] and Krishnamurthy et al. [1] and Beaudet disturbances. Note that Kumar [9], Mutiso [20] and Burton et et al. [31], point at the need of developing conceptual models al. [21] cautioned that if disturbances are beyond a certain of forest response to changes in disturbance severity. Such critical limit, the ecosystem can “flip” off into an alternative models will show equilibrial attractors and give insights on state to the detriment of all the biota in habitation. how a given landform will support a successional complex of Regaining pre-disturbance stand composition and species after disturbance and whether the expected change diversity gives the ecosystem the much needed high will be continuous, discontinuous or cusp. redundancy and resilience to future disturbances. High Sampling Design and Data Collection Techniques ecosystem redundancy cushions ecosystem against species The two study sites (Mt Blackett and Kedowa) were collapse in case of perturbation. Many tropical forests are selected subjectively to represent the disturbed and intact losing their ability for self-renewal and maintenance because sites of the Western Mau block. In Mt Blackett, four of anthropogenic perturbation [2]. Mutangah et al. [22] state transects were established on the Eastern, Western, Northern that Mau ecosystem may take many years to regain its and Southern parts of the hill while in Kedowa two transects pre-disturbance stand structure. Similar sentiments are were established on the western and Northern sides of shared by Mwangi et al. [23] who described the Mau Kedowa forest (Figure 1). Each transect, measuring 20 m by ecosystem as a sea of Neoboutonia macrocalyx(Pax) with 250 m was subdivided into 10 m by 10 m plots. A GPS isolated stands of Juniperus procera several years after receiver was used to collect UTM coordinates of the corners disturbances. Elsewhere, UNEP [24] observed dominance of of transects and the plot centres to aid in future monitoring. Cassipourea malosana (Bak) Alston, Juniperus procera The plots were further subdivided into 2 m by 5 m subplots (Endl.) and Podocarpus spp in Mt Kenya forest. Similar and the subplots subdivided into 1 m by 2 m microplots. observations were made in the upper Amazonian forest Complete enumeration was done on these data collection where species appeared to be restricted to a single forest type units. [25]. Similarly, Sapkota et al. [10] concluded that In each plot, the dbh of all individual stems (dbh ≥ 5 cm) disturbances favoured single species regeneration. Mwangi in the plot was measured. Subplots were used to capture dbh [26] documented that though the Mau ecosystem showed of all saplings (≥1- <5 cm) while microplots were used to signs of recovery after evictions of the “Ndorobos”, it will facilitate seedlings (dbh <1cm) count. The recorded take along time to regain its pre-disturbance stand structure. individual stems were categorized into various life forms: Further, there is concern over the recovery process after shrubs (< 5cm height at maturity), small trees (5-20m height recent studies; [12] revealed individualistic successional at maturity), large trees (>20m height at maturity) and pathway in Mau characterized by invasive species such as climbers. All the data collected were recorded in prescribed Trichlodus ellipticus. The study also questioned the field data collection forms. aggressiveness and persistent existence of pioneers